In recent years, the various physiological activities have become known as have the importance of peptides as medical supplies for medical treatment, diagnosis or other uses and as seasoning agents. Accordingly, there has been a great deal of development of the processes for synthesizing peptides. Chief processes for synthesizing peptides which are now known can be classified into chemical synthesis processes and enzymatic synthesis processes as described in Pharmacia Review, No. 3, pages 27-47 (1980). The chemical synthesis processes include condensing amino acids one by one by an azide process, a mixed acid anhydride process, an active ester process or a carbodiimide process and a process which comprises condensing with fragments. However, in any of these chemical synthesis processes, there are various problems. More specifically, racemization and side reactions are easily caused and the reaction time is long and the end amino group must be previously protected with a protective group before the reaction. With respect to the fragment condensation process, there is a serious fault in that racemization is particularly easily caused.
In order to avoid the occurrence of racemization as much as possible, an enzymatic synthesis process using protease has been proposed in U.S. Pat. No. 4,119,493. In this process, however, complexity of operation is still not improved, because the reaction time is long and the end amino group must be protected. Further, the enzymatic synthesis process using protease has a serious fault in that the desired peptide cannot be obtained frequently, because the formed peptide is decomposed during synthesis thereof. This occurs because the enzyme used has an inherent activity which involves decomposing peptides. Particularly, when applying this process to the synthesis of and oligopeptide, there is a serious fault in that undesired peptides are obtained wherein a part of the amino acids are lacking in Journal of Biological Chemistry, Vol. 256, page 1301 (1981). A known process for synthesizing peptides by enzymatic synthesis involves using a special enzyme which synthesizes only one peptide having a specified amino acid arrangement, in addition to the protease process. Examples of such enzymes include glutathione synthesizing enzyme which synthesizes tripeptide having an arrangement of glutamic acid/cystein/glycine as described in Japanese Patent Application (OPI) No. 122793/79 (The term "OPI" as used herein refers to a "published unexamined Japanese patent application".) and gramicidin S synthesizing enzymes which synthesize gramicidin S of decapeptide as described in Gendai Kagaku, December 1974, page 12. However, these enzymes are special ones and a desired suitable peptide can not be synthesized because only one limited kind of peptide is synthesized by them. Therefore, under existing circumstances, this process can not be used as a general process for synthesizing peptides.